XML 30 R81.htm IDEA: XBRL DOCUMENT v2.4.0.6
Employee Benefits - Additional Information (Detail) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2011
Dec. 31, 2010
Dec. 31, 2009
Employee Benefits Disclosure [Line Items]      
Cash contributions to 401(K) plan $ 4.6 $ 3.1 $ 2.8